The subject matter of the invention relates to a polymeric transition-metal complex catalyst with organosiloxane phenylphosphine ligands which are present as formed copolycondensates. The formed, polymeric, insoluble complex compounds of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and/or Pt exhibit the engineering and application-technology advantages of a macroscopic spherical form and have the physical properties necessary for use as a heterogenized complex catalyst. Additionally, methods are described herein whereby the products can be prepared, not only in the spherical size desired for the particular use, but also with the suitable physical properties. In addition, the use of these polymeric catalysts is described.
Homogeneous catalysts that are used exhibit, without exception, a higher activity and selectivity than comparable heterogeneous catalysts. However, rather significant engineering problems generally occur in the use of these catalysts in connection with their separation of the formed product from solvent present and with their recycling. Moreover, the recovery of the expensive noble-metal component from the residue of the reaction mixture is expensive and can normally only be carried out only with rather significant metal losses.
In many instances, another disadvantage of homogeneous catalysts that are used is the rather short residence time, which is caused by the formation of catalytically inactive species.
In order to circumvent these disadvantages of the homogeneous catalysts, so-called "heterogenized homogeneous catalysts" or "heterogenized catalysts" have been developed. In these catalyst, the normally homogeneous catalyst is bound to a solid carrier. These catalysts have already been used for some time worldwide.
The state of the art in this area of catalysis has already been multiply summarized in the appropriate survey literature, e.g. by R. H. Grubbs in CHEMTECH, August 1977, p. 512; by F. R. Hartley in "Catalysis by Metal Complexes", D. Reidel Publ. Co., 1985; or also by Yu. I. Yermakov et al. in "Catalysis by Supported Complexes", Elsevier Scientific Publ. Co., 1981. These literature citations are entirely incorporated herein by reference.
However, up to the present time, for a number of reasons, the organic and inorganic polymer systems used as carrier materials have met the desired requirements only to a very limited extent. In particular, in the case of the organic polymer carriers, the physical and mechanical properties, as well as the unacceptably low chemical stability, represent disadvantages. With regard to the inorganic polymer carriers, such as silica gel, these carriers have the disadvantage of a low ability to be functionalized and, in addition, are insufficiently defined.
Novel, heterogenized metal complex catalysts which do not exhibit these disadvantages of the previous systems were recently developed, as in described in German patent 30 29 599, which is entirely incorporated herein by reference. The matrix of these polysiloxane catalysts practically has the advantages of an inorganic polymer carrier and, in addition, can be produced approximately on a made to order basis in accordance with the requirements of the particular system. For example, with regard to the important aspects of the catalysts, the metal:ligand ratio can be varied; the cross-linking agents can be integrated into the matrix; or the catalytic central density and distribution can be controlled. Compared to systems with purely inorganic carriers, these organopolysiloxane polymers display the advantages of a higher metal concentration, a simpler preparative accessibility and a greater stability vis-a-vis chemical degradation.
In particular, the polymeric metal phosphine complexes mentioned in German patent 30 29 599, which generally exhibit very good catalytic properties, were synthesized according to this concept. However, these heterogenized complex catalysts have the disadvantage that previously they could be prepared only in a relatively undefined macroscopic shape, and not in the spherical form advantageous in application technology, with the desired physical and morphological properties.